Feb. 11, 2005 TinyOS Technology Exchange 1

Storage Abstractionsin TinyOS 2.x

Jonathan Huijwhui@cs.berkeley.edu

University of California, Berkeley

David Gaydgay@acm.org

Intel Research, Berkeley

TinyOS Technology Exchange 2Feb. 11, 2005

Non-Volatile Storage

Flash storage becoming more widely used“Mass” data storage

logging sensor data network programming event logging for debugging

Configuration data that survives power-failure reprogramming

TinyOS Technology Exchange 3Feb. 11, 2005

Flash Storage Variety

STMicro M25P (NOR)Telos rev. B, Eyes 1

Intel StrataFlash (NOR) iMote 2

Atmel AT45DB (NOR)Mica Family, Telos rev. A, Eyes 2But has very different characteristics

TinyOS Technology Exchange 4Feb. 11, 2005

Technology Differences

NOR AT45DB NAND

Erase Slow (seconds) Fast (ms) Fast (ms)

Erase Unit Large (64K-128K) Small (256) Medium (8K-32K)

Writes Slow (100 kB/s) Slow (60 kB/s) Fast (MB/s)

Write Unit 1 bit 256 bytes 100’s bytes

Bit-Errors Low Low High (requires ECC)

Read Fast Slow + I/O Bus Fast + I/O Bus

Erase Cycles 10^4 – 10^5 10^4 10^5 – 10^7

Intended Use Code storage Data storage Data storage

One write per bit per erase cycle Flash characteristics:

Not used in current motes

TinyOS Technology Exchange 5Feb. 11, 2005

Architecture

Differences + limited RAM preclude common low-level HIL interfaces (e.g. block interface)

Provide high-level storage services useful for sensor network applications Large Objects Small Objects Large Sequential Objects

Separate implementations of these abstractions for each class of storage chip

TinyOS Technology Exchange 6Feb. 11, 2005

Large Objects

Get a large object, write to each byte once in any arbitrary order, and commit.

Characteristics Size: Large (100B to 100KB, or more) Reads: random Writes: random (write once) Fault tolerance: validity check

Example Applications Network Programming Large Data Transfer

TinyOS Technology Exchange 7Feb. 11, 2005

Small Objects

Maintain a small chunk of values. Requires multiple and random reads/writes.

Characteristics Size: Small (< 100B) Reads: random Writes: random Fault tolerance: writes are atomic

Failure between/during writes no data loss

Example Applications: Configuration data storage

TinyOS Technology Exchange 8Feb. 11, 2005

Large Sequential Object

Some applications (e.g., low-rate data collection) may want to reliably log all their results.

Characteristics Size: Large Reads: sequential Writes: sequential Fault tolerance: user-specified commit points

Failure between/during writes entire object is not lost

Example Applications Logging

TinyOS Technology Exchange 9Feb. 11, 2005

Putting It Together

Sharing the flash through Volumes, with numerical identifiers

Volumes allocated similar to using fdisk. A utility explicitly “formats” the flash.

1) Init volume table

2) Allocate each desired volume (user specifies UID and size)

3) Commit volume table

Volume table kept in non-volatile storage.

Volume 0 Volume 1 Volume 2 Volume 3Flash

TinyOS Technology Exchange 10Feb. 11, 2005

Putting It Together

TinyOS apps must mount volume before use. Mount by specifying UID of volume No unmount operation

A volume is used by at most one HIL. Allows switching of applications while managing

the sharing of flash.

Volume 0 Volume 1 Volume 2 Volume 3

Small Object Large Object Log Log

Flash

TinyOS Technology Exchange 11Feb. 11, 2005

Implementation Status

Currently under development:AT45DB – Mica family, Telos rev. A, Eyes 2STM25P – Telos rev. B, Eyes 1

Alpha (incomplete, etc) code on SourceForge, in: tinyos-2.x/tos/chips/at45db tinyos-2.x/tos/chips/stm25p

Thanks!

TinyOS Technology Exchange 12Feb. 11, 2005

Backup Slides

TinyOS Technology Exchange 13Feb. 11, 2005

BlockStorage

interface BlockRead { command result_t read(addr_t addr, void* dest, addr_t len); event void readDone(storage_result_t result); command result_t verify(); event void verifyDone(storage_result_t result); }

interface BlockWrite { command result_t write(addr_t addr, void* source, addr_t len); event void writeDone(storage_result_t result); command result_t erase(); event void eraseDone(storage_result_t result); command result_t commit(); event void commitDone(storage_result_t result); }

TinyOS Technology Exchange 14Feb. 11, 2005

ConfigStorage

interface ConfigStorage { command result_t read(addr_t addr, void* dest, addr_t len); event void readDone(storage_result_t result);

command result_t write(addr_t addr void* source, addr_t len); event void writeDone(storage_result_t result);

command result_t commit(); event void commitDone(storage_result_t result); }

TinyOS Technology Exchange 15Feb. 11, 2005

Logger

interface LogRead { command result_t read(uint8_t* data, uint32_t numBytes); event void readDone(uint8_t* data, uint32_t numBytes, storage_result_t success); command result_t seek(uint32_t cookie); event void seekDone(storage_result_t success); }

interface LogWrite { command result_t erase(); event void eraseDone(storage_result_t success); command result_t append(uint8_t* data, uint32_t numBytes); event void appendDone(uint8_t* data, uint32_t numBytes, storage_result_t success); command uint32_t currentOffset(); command result_t sync(); event void syncDone(storage_result_t success); }

TinyOS Technology Exchange 16Feb. 11, 2005

Volume Management

interface FStorage { command result_t init(); command result_t allocate(uint8_t id, addr_t size); command result_t allocateFixed(uint8_t id, addr_t addr,

addr_t size); command result_t commit(); event void commitDone(storage_result_t result, uint8_t id); }

interface Mount { command result_t mount(uint8_t id); event void mountDone(storage_result_t result, uint8_t id); }